2002 Boxster S 986 : MOT Emissions Failure
 

Hi,

My car has just failed its MOT on exhaust emissions. :(

The acceptable lambda range is listed as between 0.97 and 1.03.

My car tested at Lambda 1.06.

The test is listed as High Idle (3,071rpm) ,it appears to have passed the low idle (680 rpm)

I have no lights on the dash and have connected up my ODB reader (Torque Andriod) and have no codes stored on the car.

I would be very gratefull if anyone can point me in the direction as to what my problem may be, as I dont want to spend a fortune on the car at a dealer if at all possible.

In the past three months I changed all the spark plugs and coils packs and the car has covered 6000km with no faults.

I presume it is safe to continue driving the car?

Thanks!

With no codes the car thinks everything is within acceptable parameters.

Check the cheap things first if it is the emissions out of limit and not just a faulty sensor:

Check the engine air filter.
Clean the MAF sensor with ONLY a MAF cleaner.
Check for air leaks in the induction system and all hoses connected to it.
Check for Exhaust header leaks.

Did they identify which lambda sensor was reading too high? A faulty sensor?
There are 4 sensors and easy to replace if they are known to be bad, but a little pricey if you have to do all 4.

Its a common error to replace a sensor when it is not at fault but the reading was out of spec due to an engine air/fuel issue.

Without a code or diagnostic reading of the long term and short term fuel trims its hard to figure out what is going on.

Thanks for your reply.

No they only tested with a probe in the exhaust to get the lamda readings for the test so no actual tests were performed on the O2 sensors themselves.

Agree it is difficult to with any codes being thrown to point in the direction as to what the cause is.

I will def check the air filter and MAF.

How hot was the engine? the Cats work best when they are really hot. If they let it sit for an hour and then brought the car in for testing, that might make a difference. You might also want to try cleaning the intake.

These are just the basics.
Good luck.
Tony

He lives in Ireland (ROW spec) where they have only have 2 cats / sensors to check or replace.
That makes it a little easier on the checking and or wallet.....

My first thought when reading reading this was to wonder what if the cam deviations are in spec due to worn chain pads. Do you happen to know what the chain devition is or could anyone comment if they would cause this probelm?